We fitted the visibility data with a 2D Gaussian in order to find the half-flux radii (HWHM) of the pure Br\(\gamma \)  emission region, using the inclination and position angles of the K-band continuum emission region presented in [1]} to constrain those two parameters in our fit.
The HWHMs we obtained through this process are, across the entire sample, on the order of less than 0.21 au at their greatest extent, ranging down to regions as compact as 0.03 au. In terms of stellar radii, the central channel sizes vary from up to 13 R\(_*\)  to less than 5 \(R_*\) , although the majority of objects show clustering (see Figures REF , REF ) in a range from 4 to 7 R\(_*\) , which is fairly typical for magnetospheric radii [2]}. This clustering can be observed across the entire range of mass accretion rates of our small sample, so that a correlation between those sizes and accretion rates cannot be established here. Equally, within our sample we do not detect a clear correlation of those Br\(\gamma \)  sizes with the luminosity of the objects, as opposed to the NIR continuum sizes, which were shown to correlate as per R \(\propto \)  L\(^{1/2}\)  [1]}. However, it is apparent from Fig. REF  that the two weakest accretors in the sample (TW Hya, DoAr 44) also show most clearly an emission region smaller than the corotation radius, whereas most of the other objects show Br\(\gamma \)  emission coming from beyond the corotation radius.
